SAINT LOUIS (May 18, 2014) -- Irina Krush has decided to play this one out.

Only one round remains in the 2014 U.S. Women’s Championship, though for a moment, it wasn’t entirely clear the extra day would be needed. The five-time reigning champion Krush skidded into the Chess Club and Scholastic Center of Saint Louis on Saturday afternoon, having just suffered three straight draws and falling a full point behind the leader’s pace.

Sobering the mood even more was the woman who sat in front of her - both in the standings and now across the board: Anna Zatonskih, Krush’s enemy No. 1 and a four-time champion herself, ready to call it halves on their decade-long rivalry.

And like everyone else, Krush could do the math: Saturday was win or go home.

But she answered the call in Monday’s round 8, taking early advantage as white and spending the rest of the 75-move thriller slowly squeezing out any hope for a draw. The result knots the two in first place with 6/8, and also allowed Tatev Abrahamyan (5.5/8) into the fold after her win over Ashritha Eswaran.

Monday’s round 9 will settle matters: Zatonskih takes white against Katerina Nemcova (4.5/8), Krush defends as black against Viktorija Ni (3/8), as does Abrahamyan against Camilla Baginskaite (1.5/8). If necessary, a playoff is scheduled for Tuesday. The women’s tournament takes a scheduled rest day Sunday.

There is also a share for the lead atop the U.S. Championship, as time dwindles away with two rounds remaining. Varuzhan Akobian entered Saturday in clear first by a full point but never got comfortable in his eventual loss - his first of the tournament - to Sam Shankland.

Akobian stays in first with 6/9, though now shares the position after Aleksandr Lenderman caught pace after materializing a surprising win from a drawn-looking position against Daniel Naroditsky.

Reigning champion Gata Kamsky - unbeaten, yet only at +1 through 9 rounds - picked up another draw with Mackenzie Molner and now trails a half-point behind the leaders in third place (5.5/9).

Also in third place is 2013 U.S. Open winner Josh Friedel, the lowest-rated player in the field who has quietly turned in 3.5 points across the last 4 rounds to enter the fray.

The final two rounds of the U.S. Championship promise a web of matchups between the four leaders, including Sunday’s headliner between Akobian and Kamsky.

Krush was certainly no stranger to pivotal matchups with Zatonskih, and Monday’s game left little doubt as to what hung in the balance.

“Of course it was a must-win,” Krush said. “If you want to do anything in this championship, it’s a must-win. You can’t ask other people to do your work for you.

“I had sort of fallen asleep for a few rounds there, and woken up in this situation. The minimum I could do to get this tournament back on track is to win today, because otherwise I just wouldn’t deserve to be the champion.”

Though both players seemed lost early through the Catalan line, Krush was instantly the aggressor, skirting the early center fight and wrecking black’s queenside in the opening. After 13. Rxc4 cleaned up the early tactical swap of the queens and minor pieces, Zatonskih opted out of castling to protect her isolated c-pawn with 13...Kd7. It soon became the focus of Krush’s attention.

Pressing for a draw while Krush pressed for a win, Zatonskih eventually bailed on the weakness with 35...c4 to swap it out - though white simply refocused its forces on the also isolated a-pawn. Krush converted to a material advantage with 39. Rxa7.

Black’s e-pawn passer still gave chances, however, through the majority of a long rook-and-bishop endgame that challenged both players on the clock. 70...Ra8 was an interesting idea to bring black’s pawn to promotion, though ultimately failed when Krush sacked her rook at 71. Rxe2 to eliminate the threat. Black’s remaining rook was powerless to stop the connected pawns.

“I had a bad position out of the opening; I was surprised,” Zatonskih said. “I had this planned for white, I just forgot the lines. I just completely don’t remember them.

“(Krush) has improved her endgame dramatically recently. Before, it was worse, but now ...”

Shankland may no longer be in the race for the national title, but it doesn’t leave him any less dangerous of an opponent: Tension has filled each one of his games this tournament, his adversaries holding their breath on what kind of opening-book potion he might have concocted just for them. The 22-year-old had already reached into his bag of tricks in round 6 to knock then-leader Lenderman from his pedestal, and on Saturday he did it again to another frontrunner in Akobian.

Akobian defended in the Caro-Kann and admitted displeasure with white’s 7.c3, exemplified by his awkward 10...Bc5 that left the piece useless and wandering through much of the middlegame. Starting with 15...Be7, where the dark-squared bishop likely should have first moved, Akobian moved the piece five times in six moves.

The leak of tempo was an over-reliance on the solidarity of the Caro-Kann structure. As a result, black’s king never made it out of the center, and Akobian later lamented on missing the opportunity to play h5. White occupied the square instead at move 20, leaving black’s kingside in distress.

Challenged on the clock from the opening, Akobian was under two minutes still with ten moves to go before the 40-move time control, and his army collapsed in a hot mess under the pressure. His 28...g5 was an awkward-looking push, though his 29...d4 only served to open the board and reveal his uncoordinated pieces. In the undoing, Akobian’s queen found itself trapped by pawns on the queenside, requiring a sacrifice of his bishop at 35...Bxb4.

“(Var) pointed out that c3 is not the most challenging theoretically, and it doesn’t have the highest reputation - but i think it’s actually dangerous and I had some new ideas,” Shankland said. “It’s very sharp and for black to equalize, he has to really know his stuff and play into the sharp stuff, which can be very intimidating if you don’t know it. He played this strange-looking move Bc5, and very quickly I was quite comfortable with my position.”

The U.S. Women’s Championship enters its final rest day today. The live broadcast of round 10 of the U.S. Championship will begin at 1 p.m. CT, 2 p.m. ET on uschesschamps.com/live